Continuous method for manufacturing polycarbonate

ABSTRACT

To provide a method with which a polycarbonate can be manufactured efficiently without any pipe clogging or foreign material admixture in the course of the continuous manufacture of a polycarbonate. 
     A continuous method for manufacturing a polycarbonate, characterized in that, in the continuous manufacture of a polycarbonate by transesterification from a dihydroxy compound and a carbonic diester, 
     the crystallization of a polycarbonate lower polycondensate produced in the intermediate stage of a polycondensation reaction whose intrinsic viscosity (IV) measured at 20° C. in methylene chloride is between 0.1 and 0.4 dL/g is suppressed by setting the temperature to be at least 230° C. on the surface of the reactor equipment in contact with the polycarbonate lower polycondensate.

This is a continuation of application Ser. No. 09/464,138 filed on Dec.16, 1999, which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present application is a U.S. non-provisional application based uponand claiming priority from Japanese Application No. HEI 10-374458, whichis hereby incorporated by reference.

The present invention relates to a continuous polycarbonatemanufacturing method in which a polycarbonate with few admixtures ismanufactured continuously, stably, and efficiently.

Polycarbonates have excellent mechanical properties such as impactresistance, as well as excellent heat resistance, transparency and otherproperties. They are widely used in applications such as various typesof mechanical components, optical disks, and automotive parts. They areparticularly promising for optical applications such as miemory-useoptical disks, optical fibers, and lenses.

Known methods for manufacturing these polycarbonates include a method inwhich a bisphenol such as bisphenol A is allowed to react directly withphosgene (interfacial method), and a method in which a bisphenol such asbisphenol A is subjected to a melt polyconciensation reaction(transesterification reaction) with a carbonic faiester s uch asdiphenyl carbonate.

Of these two, the interfacial method using, phosgene is the morecommonly implemented. On tLhe other hand, an advantage of thetransesterification method is that a polycarbonate can be manulfacturedmore inexpensively than with the interfacial method, and becausetransesterification does not invole the use of a toxic substance such asphosgene, it is very promising as a polycarbonate manufacturing method.

Still, if the manufacture of a polycarbonate is carried out continuouslyover an extended period by this transesterification method, whiteforeign material can become admixed in the manufactured polycarbonateand can clog the piping lines, thereby lowering the manufacturingefficiency.

As a result of diligent research conducted in light of these problems,the inventors discovered that the lower polycarbonate polycondensateproduced in the intermediate stage of a polycondensation reaction cancrystallize when heated and become a source of white foreign material,and can crystallize on the pipe surfaces and become a cause of pipeclogging.

Upon further research, the inventors arrived at the present inventionupon discovering that a lower polycarbonate polycondensate having anintrinsic viscosity between 0.1 and 0.4 dL/g readily undergoescrystallization at temperatures below 230° C., and therefore found thatif the polycondensation of a polycarbonate is carried out by setting thetemperature to be at least 230° C. on the surface of the reactionecluipmnent in direct contact with a lower polycarbonate polycondensatehaving an intrinsic viscosity between 0.1 and 0.4 dL/g, then theadmixture of white foreign material and the clogging of the piping dueto polycarbonate crystallization will be suppressed, and a polycarbonatewith excellent hue stability will be obtained efficiently.

BRIEF SUMMARY OF THE INVENTION

The present invention was conceived on the basis of the above-mentionedproblems, and provides a method with wvlich a polycarbonate can bemanufactured efficiently without any pipe clogging or foreign materialadmixture in the course of the continuous manufacture of apolycarbonate.

The continuous method for manufacturing a polycarbonate pertaining tothe present invention is characterized in that, in the continuousmanufacture of a polycarbonate by transesterification from a dihydroxycompound and a carbonic diester, the crystallization of a polycarbonatelower polycondensate produced in the intermediate stage of apolycondensation reaction whose intrinsic viscosity (IV) measured at 20°C. in metlhylene chloride is between 0.1 and 0.4 dL/g is suppressed bysetting the temperature to be at least 230°C. on the surface of thereactor equipment in contact with the polycarbonate lowerpolycondensate.

DETAILED DESCRIPTION OF THE INVENTION

The continuous method for manufacturing a polycarbonate pertaining tothe present invention will now be described in specific terms.

The continuous method for manufacturing a polycarbonate pertaining tothe present invention is characterized in that the crystallization of apolycarbonate lower polycondensate produced in the intermediate stage ofa polycondensation reaction whose intrinsic viscosity (IV) measured at20° C. in methylene chloride is between 0.1 and 0.4 dL/g is suppressedby setting the temperature to be at least 230° C. on the surface of thereactor equipment in contact with the polycarbonate lowerpolycondensate.

First, the raw materials used in the manufacture of a polycarbonate bytransesterification will be described.

Polycarbonate Polycondensation Raw Materials

The raw materials used in the polycarbonate manufacturing methodpertaining to the present invention are a bisphenol, a carbonic diester,and an alkaline compound catalyst. Preferred bisphenols have thefollowing formula (I).

Bisphenol

(In the formula, R^(a) and R^(b) are the same or different, and are eacha halogen atom or a univalent hydrocarbon group. p and q are integersfrom 0 to 4. X is

or

R^(c) and R^(d) are each a hydrogen atom or a univalent hydrocarbongroup, R^(c) and R^(d) may form a ring structure, and R^(e) is adivalent hydrocarbon group.)

Specific examples of the bisphenols expressed by the above formula (I)include:

bis(hydroxyaryl)alkanes such as:

1,1-bis(4-hydroxyphenyl)methane,

1,1-bis(4-hydroxyphenyl)ethane,

2,2-bis(4-hydroxyphenyl)propane (hereinafter referred to as bisphenolA),

2,2-bis(4-hydroxyphenyl)-butane,

2,2-bis(4-hydroxyphenyl)octane,

1,1-bis(4-hydroxyphenyl)propane,

1,1-bis(4-hydroxyphenyl)n-butane,

bis(4-hydroxyphenyl)phenylmethane,

2,2-bis(4-hydroxy-1-methylphenyl)propane,

1,1-bis(4-hydroxy-t-butylphenyl)propane, and

2,2-bis(4-hydroxy-3-bromophenyl)propane; and

bis-(hydroxyaryl)cycloalkanes such as:

1,1-bis (hydroxyphenyl)cyclopentane and

1,1-bis(4-hydroxyphenyl)cyclohexane.

Other bisphenols that can be used with the present invention are thosein which X in the above formula is —O—, —S—, —SO—, or —SO₂—, examples ofwhich include:

dihydroxyaryl ethers such as:

4,4′-dihydroxydiphenyl ether and

4,4′-dihydroxy-3,3′-dimethyiphenyl ether;

dihydroxydiaryl sulfides such as:

4,4′-dihydroxydiphenyl sulfide and

4,4′-dihydroxy-3,3′-dimethyldiphenyl sulfide;

dihydroxydiaryl sulfoxides such as:

4,4′-dihydroxydiphenyl sulfoxide and

4,4′-dihydroxy-33,′-dimethyldiplienyl sulfoxide; and

dihydroxydiarylsulfones such as:

4,4′-dihydroxydiphenylsulfone and

4,4′-dihydroxy-3,3′-dimethyldiphenylsulfone.

Other examples of bisphenols are the compounds expressed by thefollowing formula (II).

(In the formula, R^(f) is a halogen atom or a C₁ to C₁₀ hydrocarbongroup or halogen-substituted hydrocarbon group, and n is an integer from0 to 4. When n is equal to or greater than 2, the R^(f) groups may bethe same or different.)

Specific examples of the bisphenols expressed by this formula (II)include:

resorcin and substituted resorcins such as 3-methylresorcin,3-ethylresorcin, 3-propylresorcin, 3-butylresorcin, 3-t-butylresorcin,3-phenylresorcin, 3-cumylresorcin, 2,3,4,6-tetrafluororesorcin, and2,3,4,6-tetrabromoresorcin;

catechol; and

hydroquinone and substituted hydroqluiniones such as3-methylhydroquinone, 3-ethylhydroquinone, 3-propylhydroquinone,3-butylhydroquinone, 3-t-butylhydro-quinone, 3-phenyihydroquinone,3-cumylhydroquinone, 2,3,5,6-tetramethylhydroquinone, and2,3,5,6-tetra-t-butylhydroquinone, 2,3,5,6-tetrafluorohydroquinone, and2,3,5,6-tetrabromohydroquinone.

Furthermore, the 2,2,2′,2′-tetralhydro-3,3,3′,3′-tetramethyl-1,140-spirobi-[IH-indene]-6,6′-diol expressed by the following formula (III)can also be used as the bisphenol.

Of these compounds, a bisphenol expressed by the above-mentioned formula(I) is preferable, and bisphenol A is particularly favorable.

Carbonic Diester

Specific examples of carbonic diesters that can be used include diphenylcarbonate, ditolyl carbonate, bis(chloroplIenyl) carbonate, m-cresylcarbonate, dinaphthyl carbonate, bis(diphenyl) carbona te, liethylcarbonate, dimethyl carbonate, dibutyl carbonate and dicyclolhexylcarbonate. Two or more of these can also be used together. Of these, theuse of diphenyl carbonate is particularly favorable.

These dliester carbonates may contain dlicarboxylic acids ordicarboxylic esters. In specific terms, the carbonic diester willpreferably contain no more than 50 mol%, and most preferably no morethan 30 mol%, dicarboxylic acids or dicarboxylic esters.

Examples of such dicarboxylic acids or dicarboxylic esters includeterephthalic acid, isophthalic acid, diphenyl tereplthialate, diphenylisophthalar , and oterer such aromatic dicarboxylic acids and esters;succinic acid, ,lutaric acid, adipic acid, pimelic acid, suberic acid,azclaic acid, sebacic acid, decanedioic acid, dodecanedioic acid,diphonyl sebacate, diphenyl decanedi-oate, d iphenyl dodecanedioate, andother such aliphatic dicarboxylic acids and esters; andcyclopropanedicaiboxylic acid, 1,2-cyclobutanedicarboxylic acid,1,3-cyclobutane-d licarboxylic acid, 1,2-cyclopentanedicarboxylic acid,1,3-cyclopentaneclicarboxylic acid, 1,2-cyclohexanedicarboxylic acid,1,3-cyclohexanedicarboxylic acid, 1,4-cyclohcxane-dicarboxylic acid,diphenyl cyclopropaniccdicarboxylate, diphenyl1,2-cyclobutane-dicarboxylate, diphenyl 1,3-cyclobutanedicarboxylate,diphenyl 1,2-cycloponatanedicarb-oxylate, diphenyl1,3-cyclopentanedicarboxylate, diphenyl 1,2-cyclohexanedicarboxylate,diphonyl 1,3-cyclohexanedicarboxylate, diphenyl1,4-cyclohexanedicarboxylatc , and other such alicyclic dicarboxylicacids and esters. The carbonic diester may also contain two or moretypes of these dicarboxylic acids or dicarboxylic esters.

The above-mentioned carbonic diester and bisphenol are usually mixedsuch that there will be 1.00 to 1.30 mol, and preferably 1.01 to 1.20mol, of carbonic diester per mole of bisphenol.

Melt Polycondensation Catalyst

The transesterification reaction between the above-mentioned bisphenoland carbonic diester is usually carried out in the presence of a meltpolycondensation catalyst.

The melt polycondensation catalyst is usually an alkali metal compoundand/or an alkaline earth metal compound (a) (hereinafter referred to asalkali (alkaline earth) metal compound (a)).

Organic acid salts, inorganic acid salts, oxides, hydroxides, hydrides,alcoholates, and the like of alkali metals and alkaline earth metals canbe used favorably as the alkali (alkaline earth) metal compound (a).

Specific examples of alkali metal compounds include sodium hydroxide,potassium hydroxide, lithium hydroxide, sodium hydrogencarbonate,potassium hydrogencarbonate, lithium hydrogencarbonate, sodiumcarbonate, potassium carbonate, lithium carbonate, sodium acetate,potassium acetate, lithium acetate, sodium stearate, potassium stearate,lithium stearate, sodium boron hydride, lithium boron hydride, sodiumboron phenylate, sodium benzoate, potassium benzoate, lithium benzoate,disodlium hydrogen phosplhate, dipotassium hydrogenphosphate, dilithiumhydrogenphosphate, the disodium, dipotassium, and dilithium salts ofbisphenol A, and the sodium, potassium, and lithium salts of phenol.

Examples of alkaline earth metal compounds include calcium hydroxide,barium hydroxide, magnesium hydroxide, strontium hydroxide, calciumhydrogencarbonate, barium hydrogencarbonate, magnesiumhydrogencarbonate, strontium hydrogencar-bonate, calcium carbonate,barium carbonate, magnesium carbonate, strontium carbonate, calciumacetate, barium acetate, magnesium acetate, strontium acetate, calciumstearate, barium stearate, magnesium stearate, and strontium stearate.Two or more types of these compounds can also be used togetlher.

The alkali (alkaline earth) metal compoundc is preferably included inthe melt polycondensation reaction in an amount of 1×10⁻⁸ to 1×10⁻³ mol,and more preferably 1×10⁻⁷ to 2×10⁻⁶ mol, and particularly preferably1×10⁻⁷ to 8×10⁻⁷ mol, per mole of the bisphenol. If an alkali (alkalineearth) metal compound is contained ahead of time in the bisphenol usedas a raw material of the melt polycondensation reaction, it ispreferable for the added amount to be controlled such that the amount ofalkali (alkaline earth) metal compound present during the meltpolycondensation reaction will be within the above-mentioned range permole of the bisphenol.

A basic compound (b) may also be used together with the above-mentionedalkali (alkaline earth) metal compound (a) as the melt polycondensationcatalyst.

Examples of this basic compound (b) include nitrogen-containing basiccompounds that are volatile or readily decompose at high temperatures.The following compounds are specific examples:

Ammonium hydroxides having alkyl, aryl, aralkyl, or other such groups,such as tetramethylammonium hydroxide (Me₄NOH), tetraethylammoniumhydroxide (Et₄NOH), tetrabutylammonium hydroxide (Bu₄NOH), andtrimethylbenzylammonium hydroxide (φ—CH₂(Me)₃NOH); tertiary amines suchas trimethylamine, triethylamine, climethylbenzylamine, andtriphenylamine; secondary amines expressed by the formula R₂NH (where Ris an alkyl such as methyl or ethyl, an aryl group such as phenyl ortoluyl, or the like); primary amines expressed by the formula RNH₂(where R is the same as above); pyridines such as4-dirnethylaminopyridine, 4-ethylaminopyridine, and4-pyrol-lidinopyridine; imidazoles such as 2-methylimidazole and2-phenylimiciazole; and basic salts such as ammonia, tetramethylammoniumborohydride (Me₄NBH₄), tetrabutylammonium borohyvcride (Bu₄NBH₄),tetrabutylammonium tetraphenyl borate (Bu₄NBPh₄), andtetramethylammonium tetraphenylborate (Me₄NBPh₄).

Of these, the use of a tetraalkylammonium hydroxide is preferable.

The above-mentioned nitrogen-containing basic compound (b) can be usedin an amount of 1×10⁻⁶ to 1×10¹ mol, and preferably 1×10⁻⁵ to 1×10⁻²mol, per mole of bisphenol.

A boric acid compound (c) can also be used as the catalyst.

Examples of this boric acid compound (c) include boric acid and boricesters.

Examples of boric esters include the boric esters expressed by thefollowing General Formula (IV).

B(OR)_(n)(OH)_(3-n)  [IV]

In the formula, R is an alkyl such as methyl or ethyl, an aryl such asphenyl, or the like, and n is 1, 2, or 3.

Specific examples of boric esters such as these include trimethylborate, triethyl borate, tributyl borate, trihexyl borate, trilheptylborate, triphenyl borate, tritolyl borate, and trinaphthyl borate.

This boric acid or boric ester (c) can be used in an amiount of 1×10⁻⁸to 1×10⁻¹ mol, and preferably 1×10⁻⁷ to 1×10⁻² mol, and even morepreferably 1×10⁻⁶ to 1×10⁻⁴ mol, per mole of bisphenol.

It is preferable for the melt polycondensation catalyst to be, forexample, a combination of the alkali (alkaline earth) metal compound (a)and the nitrogen-containinog basic compound (b), and even better for itto be the three components of the alkali (alkaline earth) metal compound(a), the nitrogen-containing basic compound (b), and the boric acid orboric ester (c).

It is preferable for a combination of an alkali (alkaline earth) metalcompound (a) and a nitrogen-containing basic compound (b) to be used inthe above amounts as the catalyst because the polycondlensation reactioncan be made to proceed at a sufficient rate and a higlh molecular weightpolycarbonate can be produced at a high polymerization activity.

When the alkali (alkaline earth) metal compound (a) and thenitrogen-containing basic compound (b) are used together, or when thealkali (alkaline earth) metal compound (a), the nitrogen-containingbasic compound (b), and the boric acid compound (c) are used together, amixture of the various catalyst components may be added to a moltenmixture of a bisphenol and a carbonic diester, or they may be addedindividually to a molten mixture of a bisphenol and a carbonic diester.

The above-mentioned bisphenol and carbonic diester are subjected to meltpolycondensation in the presence of the above-mentioned meltpolycondensation catalyst. Microparticles and other such impurities maybe removed ahead of time from the liquid mixture of the bisphenol andthe carbonic diester by using a fluororesin membrane filter.

The polycondensation reaction of the bisplhenol and the carbonic diestercan be conducted under the same conditions as those known in the pastfor polycondensation reactions. For instance, it can be conducted in twoor more reaction stages.

Specifically, in the first stage reaction the lbisphenol and thecarbonic diester are allowed to react under normal pressure, at atemperature of 80 to 250° C., and preferably 100 to 230° C., anld evenmore preferably 120 to 190° C., for a time of 0.01 to 5 hours, andpreferably 0.01 to 4 hours, and even more preferably 0.01 to 3 hours.The reaction temperature is then raised while the reaction system isreduced in pressure so as to brine, about a reaction between thebisphenol and the carbonic diester, and finally a polycondensationreaction between the bisphenol and the carbonic diester is conducted at240 to 320° C. under reduced pressure of 5 mmHg, or less, andicpreferably 1 mmHg or less.

In the manufacture of the polycarbonate, a polyfunctional compoundhaving three or more functional groups per molecule may be used alongwith the above-mentioned bisphenol and carbonic diester. Thispolyfunctional compound is preferably a compound having phesndolichydroxyl groups or carboxyl groups, with a compound having threephenolic hydroxyl groups being especially desirable. Examples include1,1,1-tris(4-hydroxyphenyl)-ethane,2,2′,2″-tris(4-hydroxyphenyl)diisopropylbenzene, α-methyl-α,α′,α′-tris(4-hydroxyphenyl)-1,4-diethylbenzene, α,α′,α″-tris(4-hydroxyphen-yl)-1,3,5-triisopropylbenzene, fluoroglycine,4,6-dimethyl-2,4,6-tri(4-hydroxyphenyl)hep-tane-2,1,3,5-tri(4-hydroxypheiiyl)benzene,2,2-bis-[4,4-(4,4′-dihydroxyphenyl)-cyclo-hexyl]propane, trimelliticacid, 1,3,5-benzenctricarboxylic acid, and pyromellitic acid.

Of these, the use of 1,1,1-tris(4-hydroxypheniyl)-ethane, α,α′,α″-tris(4-hydroxy-phenyl)-1,3,5-triisopropylbenzene, or the like ispreferable.

This polyfunctional compound is generally used in an amount of no morethan 0.03 mol, preferably 0.001 to 0.02 mol, aind even more preferably0.001 to 0.01 mol, per mole of the bisphenol.

A terminal capping agent may be used along, with the above-mentionedaromatic dihydroxy compound and the carbonic dilester in the manufactureof the polycarbonate.

An allyloxy compound capable of introducing a terminal group expressedby the following General Formula V at the molecular terminal of theobtained polycarboniate can be used as this terminal capping agent.

In the formula, Ar is an aromatic hydrocarbon group with 6 to 50 carbonatoms. There are no particular restrictions on the aromatic hydrocarbongroup, which may be a phenyl group or naphthyl group, or an anthranylgroup or other such condensed ring, and these aromatic rings may formrings with hetero atoms and/or saturated hydrocarbons. These aromaticrings may also be substituted with a halogen or an alkyl group with 1 to9 carbon atoms.

Specific examples of this allyloxy compound include phenol, diphenylcarbonate, p-tert-butylphenol, p-tert-butylphenyl phenylcarbonate,p-tert-butyl phenylcarbonate, p-cumylphenol, p-cumylpphenylphenylcarbonate, p-cumyl phenylcarbonate,2,2,4-trimeth-yl-4-(4-hydroxyplhenyl)chroman,2,2,4,6-tetramethyl-4-(3,5-dimethyl-4-hlydroxypheiyl)-chronan,2,2,-trimethyl-3-(4-hydroxyp enyl)- chroman,2,4,4-trimethyl-2-(2-hydroxy-phenyl) clhroman,2,4,4,6-tetramethyl-2-(3,5-dimethyl-2-hydroxyphenyl)-chroman, and othersuch chroman compounds.

The above-mentioned allyloxy compounds can be used singly or incombinations. This allyloxy compound usually should be used in an amountof 0.01 to 0.2 mol, and preferably 0.02 to 0.15 mol, and even morepreferably 0.02 to 0.1 mol, per mole of aromatic dihydroxy compound.

When an allyloxy compound is used in the above amount as a terminalcapping agent, the molecular terminals of the polycarbonate thusobtained will be capped with end groups expressed by the above-mentionedGeneral Formula V in a proportion of 1 to 95%, and preferably 10 to 95%,and even more preferably 20 to 90%.

A polycarbonate in which end groups expressed by General Formula V havethus been introduced in the above proportion will exhibit excellent heatresistance, as well as excellent mechanical properties, such as impactresistance, even aL a low molecular weight.

An aliphatic monocarboxy compound capable of introducing aliphatichydrocarbon units expressed by the following General Formula VI may alsobe used as needed along with the above-mentioned allyloxy compound as aterminal capping agent.

In the formula, R is an alkyl with 10 to 30 carbon atoms, and may belinear or branched, and may be halogen substituted.

Specific examples of this aliphatic monocarboxy compound includeundecanoic acid, lauric acid, tridecanoic acid, pentadecanoic acid,palmitic acid, heptadecanoic acid, stearic acid, nonadecanoic acid,heneicosanoic acid, tricosanoic acid, melissic acid, and other suchalkylmonocarboxylic acids, and methyl stearate, ethyl stearate, phenylstearate, and other such methyl esters, ethyl esters, and phenyl estersof the above-mentioned alkylmonocarboxylic acids, and other suchalkylmonocarboxylic esters.

These may be used singly or in combinations.

The above-mentioned aliphatic monocarboxy coim pound usually should beused in an amount of 0.01 to 0.20 mol, and preferably 0.02 to 0.15 mol,and even more preferably 0.02 to 0.10 mol, per mole of the aromaticdihydroxy compound.

The polymerization rate may decrease if the above-mntioned terminalcapping agent is used in.a total amount of more than 0.2 mnol per moleof the aromatic dihydroxy compound.

Melt Polycondensation of the Polycarbonate

It is possible to use a known reaction apparatus in the continuousmanufacture of a polycarbonate from the above-mentioned polymerizationraw materials. It is particularly desirable to use reactors withdifferent agitation configurations in the early stage of polymerizationwhen the viscosity of the reaction product is low and in the later stageof polymerization when the viscosity is high.

Examples of these reactors include a vertically agitated polymerizationtank, a thin film evaporation polymerization tank, a vacuumpolymerization tank, a horizontally agitated polymerization tank, and atwin-screw vented extruder.

It is preferable to use two or more of these reactors combined inseries, and a particularly favorable combination is for at least one ofthe reactors to be a horizontal reactor such as a horizontally agitatedpolymerization tank. Specific examples of such combinations include avertically agitated polymerization tank and a horizontally agitatedpolymerization tank, a horizontally agitated polymerization tank and avertically agitated polymerization tank, a horizontally agitatedpolymerization tank and a horizontally agitated polymerization tank, avertically agitated polymerization tank and a vacuum polymerization tankand a horizontally agitated polymerization tank, and a thin filmevaporation polymerization tank and two horizontally agitatedpolymerization tanks.

When a combination of two or more reactors is used, it is even betterfor three or more reactors to be used in series, in which case it ispreferable for at least one of the reactors to be a horizontal reactorsuch as a horizontally agitated polymerization tank. Specific examplesof Lisinig three or more reactors in series include two or morevertically agitated polymerization tanks and one horizontally agitatedpolymerization tank, one or more vertically agitated polymerizationtanks and one thin film evaporation polymerization tank and onehorizontally agitated polymerization tank, and one or more verticallyagitated polymerization tanks and two or more horizontally agitatedpolymerization tanks.

The polycondensation reaction can be conducted more efficiently by thususing a combination of at least two reactors in series.

With the continuous method for manufacturing a polycarbonate pertainingto the present invention, the temperature is set to be at least 230° C.,and preferably at least 240° C., on the surface of the reactor equipmentin contact with the polycarbonate lower polycondensate produced in theintermediate stage of the polycondensation reaction of theabove-mentioned bisphenol and carbonic diester, wherein thispolycondeinisate has an intrinsic viscosity (IV) measured at 20° C. inmethylene chloride of between 0.1 and 0.4 dL/g.

The inventors have learned that a lower polycarbonate polycondensatewith an intrinsic viscosity between 0.1 and 0.4 dL/g has a tendencywhereby it readily undergoes crystallization at a temperature of 230° C.or higher.

This tendency is illustrated in FIG. 1, for example. FIG. 1 shows thechange in percentage crystallization as a function of temperature inpolycarbonate polycondensates with an intrinsic viscosity of 0.06 dL/g,0.18 dL/g, 0.36 dL/g, 0.46 dL/g, and 0.50 dL/g.

As is clear from FIG. 1, those polycaribonates whose intrinsic viscosityis 0.06 dL/g, 0.46 dL/g, and 0.50 dL/g all have a crystallization of 0%between 200 and 240° C., while those polycaribon,ates with an intrinsicviscosity of 0.18 dL/g and 0.36 6dL/g have a crystallization close to 0%at 230° C. and above, but have a higher crystallization at a temperaturebelow 2230° C.

Thus, a polycarbonate whose percentage crystallization is between 0.1and 0.4 dL/g readily crystallizes at a temperature under 230° C., andtherefore if the surface temperature of the reactor equipment in directcontact with a polycarbonate having an intrinsic viscosity between 0.1and 0.4 dL/g is set to 230° C. or higher, the crystallization of thepolycarbonate will be suppressed, polycarbonate crystals will not beadmixed as foreign material and the pipes will not become clogged, and apolycarbonate with excellent hue can be manufactured stably andcontinuously.

Examples of reactor equipment that comes into direct contact with apolycarbonate such as this include the polymerization tank, agitationimpeller, piping, heat exchanger, and filter.

There are no particular restrictions on the method for setting thesurface temperature of this reactor equipment to 230° C. or higher, butan example is to raise the temperature of the reaction tank itself. Inthe case of piping, a heater may be installed around the pipes. Thepolymerization tank, pipes, heat exchanger, and the like may also becovered with a thermal insulation material so that the surfacetemperature will not drop during the melt polycondensation.

The melt flow rate of the reaction product (polycarbonate) obtained bythe manufacturing method pertaining to the present invention is 1 to 70g/10 minutes, and preferably 2 to 50 g/10 minutes, measured at atemperature of 300° C. and a load of 1.2 kg with high viscosityproducts, and is 5 to 20 g/10 minutes, and preferably 8 to 16 g/10minutes, meansured in the same manner but at a temperature of 250° C.and a load of 1.2 kgt witlh low viscosity products.

The following sulfur-containing acidic compound whose pKa is 3 or lessand/or a derivative formed from this acidic compound (hereinaftersometimes referred to as “acidic compound”) may be added immediatelyafter the polycondensation reaction, without the polycarbonate (reactionproduct) thus obtained being cooled first.

Examples of sulfur-containing acidic compounds and derivatives formedfrom these acidic compounds include sulfurous acid, sulfuric acid,sulfinic acid-based compounds, sulfonic acid-based compounds, andderivatives of these. Specific examples of include sulfurous acidderivatives include dimethylsulfurous acid, diethylsulfurous acid,dipropylsulfurous acid, dibutylsulfurous acid, and diphenylsulfurousacid.

Examples of sulfuric acid derivatives include dimethylsulfuric acid,diethylsulfuric acid, dipropylsulfuric acid, dlibutylsulfuric acid, anddiphenylsulfuric acid.

Examples of sulfinic acid-based compounds include benzenesulfinic acid,toluene-sulfinic acid, and naphthalenesulfinic acid.

Examples of sulfonic acid-based compounds and derivatives thereofinclude compounds expressed by the following General Formula VII andammonium salts thereof.

In the formula, R^(g) is a C₁ to C₅₀ hydrocarbon group or ahalogen-substituted hydrocarbon group, R^(h) is a hydrogen atom, a C₁ toC₅₀ hydrocarbon group, or a halogen-substituted hydrocarbon group, and nis an integer from 0 to 30.

Two or more types of these can be used in combiniation.

Of these acidic compounds, the use of sulfonic acid-based compoundsexpressed by the above-mentioned General Formula VII and derivativesthereof is preferable.

The polycarbonate (A) used in the present invention contains theabove-mentioned acidic compound in an amount of 0.1 to 4.5 ppm, andpreferably 0.2 to 3 ppm, with respect to the reaction product.

When an acidic compound is added in this amount to the reaction product(polycarbonate), any alkali metal compound catalyst remaining in thepolycarbonate will be neutralized or weakened (in alkalinity),ultimately allowing a polycarbonate to be obtained with further enhancedretention stability and water resistance.

Water may be added along with the above-mentioned acidic compound. Thewater should be added in an amount of 5 to 1000 ppm, and preferably 10to 500 ppm, and even more preferably 20 to 300 ppm, with respect to thereaction product (i.e., polycarbonate).

The kneading of the reaction product and the acidic compound isaccomplished with an ordinary kneader such as a single-screw extruder, atwin-screw extruder, or a static mixer. In more specific terms, it isfavorable for the acidic compound and water to be added while thereaction product obtained from the polycondensation reaction is in amolten state in the reactor or extruder.

Additives (E) may also be contained as needed. Specific examples orthese additives (E) include thermal stabilizers, epoxy compounds,ultraviolet absorbents, parting agents, colorants, antistatic agents,slip agents, anti-blocking agents, lubricants, anti-fogging agents,natural oils, synthetic oils, waxes, organic fillers, and inorganicfillers.

As discussed above, with the method for manufacturing a polycarbonatepertaining to the present invention, the polycondensation of thepolycarbonate is carried out with the surface temperature of the reactorequipment that comes into direct contact with the lower polycarbonatepolycondensate having an intrinsic viscosity between 0.1 and 0.4 dL/gset to 230° C. or higher, so the admixture of white foreign material andthe clogging of pipes due to polycarbonate crystallization aresuppressed, and a polycarbonate with superior hue stability can bemanufactured stably.

EFFECT OF THE INVENTION

With the present invention, the admixture of white foreign material andthe clogging of pipes due to polycarbonate crystallization aresuppressed, and a polycarbonate with superior hue stability can bemanufactured stably. A polycarbonate obtained in this manner can be usedfavorably in sheeting and other construction materials, automotiveheadlamp lenses, eyeglasses and other such optical lenses, and opticaldisks and other such optical recording materials.

WORKING EXAMPLES

The present invention will now be described in specific terms throughworking examples, but the present invention is not limited to or bythese examples.

WORKING EXAMPLES 1 POLYMERIZATION OF POLYCARBONATE

A polycarbonate was polymerized using one agitation tank for mixing theraw-x materials, two prepolymerizaiion tanks (prepolymerization tanks Aand B), two horizontal polymerization tanks (horizontal polymerizationtanks A and B), and pipes that connected the agitation tank withprepolymerization tank A, prepolymerization tank A withprepolymerization tank B, prepolymerization tank B with horizontalpolymerization tank A, and horizontal polymerization tank A withhorizontal polymerization tank B.

The various reaction conditions are shown in Table 1.

Molten bisphenol A pumped through a direct pipe from a bisphenol Amanufacturing apparatus (supply rate: 36.0 kg/hr), molten diphenylcarbonate pumped through a direct pipe after distillation (supply rate:34.7 kg/hr), a phenol solution containing tetra-methylammonium hydroxidein an amount of 2.5×10⁻⁵ mol per mole of bisphenol A, and a phenolsolution containing 1.0×10⁻⁶ mol sodium hydroxide per mole of bisplhenolA were continuously supplied to the agitation tank to prepare a uniformsolution.

Next, the uniform solution thus prepared was supplied at a rate of 36.0kg/hr (calculated as bisphenol A) to prepolymerization tank A,prepolymerization tank B, horizontal polymerization tank A, andhorizontal polymerization tank B, in that order, and a polycarboonatewas polycondensed continuously for over a month under the above reactionconditions.

The results are given in Table 1.

TABLE 1 Surface Average residence Reactor equipment Pressure (torr)temperature (° C.) time (hr) Polycondensation conditions Agitation tankatmospheric pressure 160 2 (nitrogen atmosphere) Prepolymerization tankA 100 230 1 Prepolymerization tank B 20 270 0.5 Horizontalpolymerization tank 2 305 0.5 A Horizontal polymerization tank 0.5 3050.5 B Polycarbonate IV (dL/g) at prepolymerization 0.06 tank A outletPolycarbonate IV (dL/g) at prepolymerization 0.18 tank B outletContinuous operating conditions nothing amiss for over 1 month Thetemperature of the pipe between prepolymerization tank B and horizontalpolymerization tank A was set to at least 230° C.

During the manufacture of the polycarbotiate, it was confirmed that thetotal (amount) of alkali metal compound andl alkaline earth metalcompound in the raw material bisphenol A and ciphenyl carbonate was nomore than 1×10⁻⁷ mol per mole of bisplhenol A.

WORKING EXAMPLE 2

A polycarbonate was manufactured in the same manner as in WorkingExample 1, except that the surface temperature of prepolymerization tankB was changed as shown in Table 2.

The results are given in Table 2.

TABLE 2 Surface Average residence Reactor equipment Pressure (torr)temperature (° C.) time (hr) Polycondensation Agitation tank atmosphericpressure 160 2 conditions (nitrogen atmosphere) Prepolymerization tank A100 230 1 Prepolymerization tank B 20 240 0.5 Horizontal polymerizationtank A 2 305 0.5 Horizontal polymerization tank B 0.5 305 0.5Polycarbonate IV (dL/g) at prepolymerization 0.06 tank A outletPolycarbonate IV (dL/g) at prepolymerization 0.17 tank B outletContinuous operating conditions nothing amiss for over 1 month Thetemperature of the pipe between prepolymerization tank B and horizontalpolymerization tank A was set to at least 230° C.

COMPARATIVE EXAMPLE 1

A polycarbonate was manufactured in the same manner as in WorkingExample 1, except the surface temperatures of prepolymerization tank Band the pipe between prepolymerization tank B and horizontalpolymerization tank A were changed as shown in Table 3.

The results are given in Table 3.

TABLE 3 Surface Average residence Reactor equipment Pressure (torr)temperature (° C.) time (hr) Polycondensation conditions Agitation tankatmospheric pressure 160 2 (nitrogen atmosphere) Prepolymerization tankA 100 210 1 Prepolymerization tank B 20 230 0.5 Horizontalpolymerization 2 305 0.5 tank A Horizontal polymerization 0.5 305 0.5tank B Polycarbonate IV (dL/g) at 0.056 prepolymerization tank A outletPolycarbonate IV (dL/g) at 0.16  prepolymerization tank B outletContinuous operating conditions White foreign material began to beadmixed in horizontal polymerization tank A on the tenth day. At onemonth, the pipe between prepolymerization tank B and horizontalpolymerization tank A was clogged. The temperature of the pipe betweenprepolymerization tank B and horizontal polyinerization tank A was setto at least 225° C.

As is clear from Tables 1 to 3, with Working Examples 1 and 2, even whenthe polycarbonate was manufactured continuously for over a month, nowhite foreign material was admixed in the manufactured polycarbonate andthere was no pipe clogging.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a graph of the temperature dependence of the polycarbonatecrystallization.

What is claimed is:
 1. A polycarbonate composition prepared by acontinuous method, which method comprises the steps of: transesterifyinga dihydroxy compound and a carbonic diester to form the polycarbonate,wherein crystalization of a lower polycarbonate polycondensate in anintermediate stage of the reaction is supressed by setting thetemperature on a surface of a reactor apparatus in contact with thelower polycarbonate polycondensate to be at least 230° C., wherein thelower polycarbonate condensate has an intrinsic viscosity (IV) measuredat 20° C. in methylene chloride of between 0.1 and 0.4 dL/g.
 2. Thepolycarbonate according to claim 1, wherein the dihydroxy compound isbisplhenol A, and the carbonic diester is diphenyl carbonate.
 3. Thepolycarbonate according to claim 1, wherein the carbonic diester isselected from the group consisting of diplhenyl carbonate, ditolylcarbonate, bis(chlorodiphenyl) carbonate, m-cresyl carbonate,dinaphthyly carbonate, bis(diphenyl) carbonate, diethyl carbonate,dimethyl carbonate, dibutyl carbonate, and dicyclohexyl carbonate, andany mixture thereof.
 4. The plycarbonate according to claim 1, whereinthe dihydroxy compound is selected from the group consisting of 1,1-bis(4-hydroxyphenyl)methane; 1,1 -bis(4-hydroxy phenyl)ethane; 2,2-bis(4-hydroxyphenyl)propane; 2,2-bis(4-hydroxN phenyl) butane; 2,2-bis(4-hydroxyphenyl)octane; 1,1 -bis(4-hydroxy phenyl)propane; 1,1-bis(4-hydroxyphenyl)n-butane; bis(4-hydroxyphelnyl)plhenylmethane;2,2-bis(4-hydroxy-1-methylphenyl)propane;1,1-bis(4-hydroxy-t-butylphenyl)propane;2,2-bis(4-hydlroxy-3-bromophenyl)propane; bis-(hydroxyaryl)cvcloalkanes,1,1-bis(hydroxyphenyl)cyclopentane; 1,1-bis(4-hydroxyphenyl)cyclohexane; dihydroxyaryl ethers such as4,4′-dihydroxydiphenyl ether; 4,4′-dihydroxy-3,3′-dichlorodiphenylether; dihydroxydiaryl sulfides; 4,4-dyhyydroxypliciyl sulfide;4,4-dihydroxy-3,3′-dimethyldiphenyl sulfide; dihydroxydliarylsulfoxides; 4,4′-dihydroxyphenyl sulfoxide;4,4-dihydirox-3,3′-dimethyidiphenyl sulfoxide; dihydroxydiarylsulfones,4,4′-dihydroxydiphenylsulfone; and4,4′-dihydroxy-3,3-dimethyldiphenylsulfone, and any mixture thereof. 5.The composition according to claim 1, wherein the reactor apparatus isselected from the group consisting of a polNmierization tank, agitatorimpeller, piping, heat exchanger, and a filter, and anv combinationthereof.